Will zendo dieters tea decrease the effectiveness of my birth control? i am taking mononessa birth control.

No: The two medications should not interact significantly. However, Zendo Dieters Tea contains mostly a plant product called Senna which stimulates your bowels to move, and does not really help at all to lose weight. It is important to note, though, that women over 150 lbs. do not get as much pregnancy protection from contraceptive pills as thinner women do.

Not an issue: Your pills are absorbed in the small gut and the tea, whose main ingredient is senna, which stimulates the large bowel. The only value the tea has is to remedy constipation and can be a problem if used chronically as you might use as a supposed method to lose weight as it is advertised but not substantiated in anything I could find.